A Bridgeless Cuk AC–DC Converter With Improved Efficiency and Uniform Current Stress Sharing

This article introduces a new Cuk AC-DC converter featuring inherent power factor correction (PFC). The input rectifier of the proposed converter can be implemented using a single industry-standard full-bridge IGBT/MOSFET module, which, together with the proposed modulation scheme, eliminates the need for traditional diode-bridge rectification. The new topology offers both continuous input and output currents. Compared to its counterparts, the proposed converter requires fewer components, both active and passive. Additionally, when enabled by the proposed switching strategy, the active full-bridge in the converter provides two parallel switching paths for conduction currents during input inductor charging, a feature absent in the counterpart bridgeless Cuk rectifiers. This reduces the current stress on the input switches to only (iin+IO)/2, compared to (iin+IO) in conventional Cuk rectifiers, thereby alleviating excessive current stress on the switching devices and minimizing conduction losses. It also enhances current sharing among the switching devices and ensures uniform current stress across the switches throughout a line-frequency cycle. These advantages contribute to a more efficient converter design with better thermal management. Furthermore, the proposed converter outperforms conventional counterparts in terms of switching device power (SDP). A prototype circuit is fabricated and tested to verify the operational analysis of the topology. The converter proves to be an efficient onboard switch-mode battery charger circuit, showcasing an efficiency of 96.7%. The converter is suitable in particular for applications where the output DC voltage must be either higher or both lower and higher than the input AC voltage.